Dynamic planning summary

It's usually used dp Several kinds of problems to be solved ：

1. Count ：

（1） How many ways to the lower right corner
（2） How many ways can sum be sum

2. Find the maximum and minimum ：

（1） The maximum number and from top left to bottom right
（2） The longest ascending subsequence

3. Seeking existence ：

（1） Take the stone , Whether the first is sure to win
（2） Can you choose k Number makes sum sum

Two ． The problem solving steps ：

1. Define the State ：（ One or two dimensions , There are several variables ）

（1） Look at the last choice
（2） How to spell the front with the last time

2. State transition equation

3. Initialize conditions and boundaries （ Tips ： Initialization is placed in for In circulation ）

4. Consider state compression

One dimensional rolling array compressed into two variables
After two-dimensional compression into one-dimensional, most of them traverse from back to front